Project Summary/Abstract Early stages of breast cancer can often be treated successfully with targeted therapy, resulting a favorable long term prognosis. However, metastatic stages are likely to manifest later on and overall survival rates drop dramatically despite attempts for intervention using conventional chemotherapies. Due to this unmet need for treatment of metastatic breast cancer, it will be imperative to improve our understanding of the metastatic process so that therapeutic intervention can be designed. I will be investigating the very early stages of the metastatic cascade, cell escape from the primary tumor. My in vitro scratch model allows for investigation of early signaling mechanisms, such as Ca2+, in regulating the initiation of an increased migratory capacity of breast cancer cells that drives tumor escape. Our previous work showing mechanisms underlying mechanically sensitive Ca2+ signaling in MCF-7 cells suggests that this mechanical scratch-wounding response activates P2Y2 receptors and resulting Ca2+ release. This study will test the hypothesis that mechanically-activated Ca2+ signaling promotes microtubule acetylation to drive breast cancer cell migration. Although collective evidence from the literature and new preliminary data support this hypothesis, these detailed mechanisms linking Ca2+ and migration through microtubule post-translational modifications (MT-PTMS) have not been shown in vitro or in vivo for breast cancer. Our approach is to first define mechanisms through which the mechanical microenvironment effects this wounding response, by testing activation of P2Y2-Ca2+ in varying in vitro elastic modulus conditions (Aim 1). We will then analyze increases in microtubule acetylation downstream of P2Y2-Ca2+ and its role in enhancing capacity for cell migration in vitro (Aim 2). This wounding- linked modulation of breast cancer cell migration will be tested in vivo by determining its effects on tumor invasion (Aim 2). We aim to understand how changes to the mechanical environment of the cell can affect this signaling pathway and resulting cell migration and tumor invasion. We propose that the well-established changes in tumor rigidity and resulting abnormal cell behaviors (e.g. migration) are acting through Ca2+ signaling and MT-PTMs. New understanding of the metastatic process will be achieved through this work and as a direct result of support through this fellowship. The training I will receive with this support will serve to enhance my previous research experience in areas such as the development of research questions, data analysis, and data interpretation. It will also add new training in confocal microscopy, cancer cell biology, and mouse tumor models to my repertoire of experimental tools. In all, I will be provided with a more broad scientific foundation to become a successful independent investigator.